Pitot probes are used to detect air speed so that accurate measurements of air speeds can be provided to the pilots of aircraft. Normally pitot probes have a pitot tubes extending forward from the aircraft in various front-mounted locations. Pitot probes have an opening at the front at the tip of the tube or most-forward portion of the probe. There are also drain holes in other locations on the body of the probe. In operation the pitot is configured to allow a slip stream of air to enter the front hole and then to an airspeed indicator within the aircraft. This indicator is an instrument that measures air pressure from the pitot probe and then translates it into airspeed.
If any of the holes on the pitot probe become clogged or otherwise plugged, the probe can be rendered non-functional. Such a condition renders the operation of any aircraft to be very unsafe. Because of the criticality of pitot probes, they are usually covered to prevent water, dirt or insects from entering the openings. It is conventional operating procedure for the covers to remain on the probes whenever the aircraft is not in use.
Conventional pitot probe covers are of two general types: heat-resistant devices; and, devices that are not heat-resistant. The heat-resistant devices typically have metal components and/or rigid high-heat resistant ceramic materials. However, most conventional pitot covers are not meant to be used in heated environments.
Examples of conventional pitot covers are found in U.S. Pat. Nos. 5,938,147, and 6,612,521, both to DeGroff (one of the inventors of the present application). Both subject patents are incorporated herein by reference, as examples of pitot tube covers for non-heated environments.
Conventionally, pitot probe covers are manually installed on the pitot tubes after flight, and then removed prior to the next flight. This is also true for the pitot covers capable of withstanding high temperature. Both types are removed as part of standard aircraft system checks and power-up.
Typically, pitot covers have warning devices. One example is a colored ribbon or streamer, with an imprinted message indicating that the device should be removed before flight. Also, standard pre-flight check lists typically include the removal of pitot tube covers. Part of the pre-flight check list involves initiating the flow of heated air from the aircraft into the pitot probe for purposes of clearing the probe. This is done by using sufficiently hot air so that contaminates are removed by incineration or vaporization. The temperature of the air going into the pitot probe and through its tube can reach over 800° F. Unfortunately, this can melt or fuse a non-heat resistant pitot cover. The result is that the pitot tube becomes clogged, rendering the aircraft unsafe for use.
Many conventional pitot tube covers, such as those discussed in the patents previously incorporated herein by reference, are not designed for high temperatures, and such designs can fail on heated pitot tubes. Even specifically designed heat-resistant pitot covers can fall under some circumstances.
Even if a pitot tube cover is not fused by the hot air induced in the pitot tube, and separates easily due to air pressure, a loose pitot cover or parts thereof can be sucked into the aircraft engine causing substantial damage. This possibility poses an even greater danger than failure of airspeed indication. Even if the damage caused is not fatal, substantial maintenance problems very often result.
Accordingly, the conventional art of pitot covers admits to substantial improvement. Such improvements would provide pitot covers that are automatically removed from pitot tubes, will not fuse to pitot openings, and cause no hazard to aircraft engines. The most desirable pitot cover system is one that is always fail-safe with regard to being automatically removed at the appropriate time.